The reduced S-1 and S-2 oxidation states of the O2-evolving complex of photosystem II: An EPR microwave power saturation study

Title:

The reduced S-1 and S-2 oxidation states of the O2-evolving complex of photosystem II: An EPR microwave power saturation study

Creator:

Koulougliotis, D.

Identifier:

https://cdk.lib.cas.cz/client/handle/uuid:47d36207-1531-4133-ae7f-959bafa58411
uuid:47d36207-1531-4133-ae7f-959bafa58411
issn:0300-3607
doi:10.1007/s11099-009-0082-8

Subject:

oxygen-evolving complex, photosystem II, power saturation, and reduced S-states

Type:

model:article and TEXT

Format:

bez média and svazek

Description:

Progressive microwave power saturation (P1/2) measurements have been performed on the tyrosine D radical (YD*) of photosystem II (PSII) in order to examine its relaxation enhancement by the oxygen-evolving complex (OEC) poised to the reduced S-1 and S-2 oxidation states by NO treatment. Analysis of the power saturation curves showed that the S-1 oxidation state of the OEC does not enhance the relaxation of YD*: it therefore possesses a diamagnetic ground state. In contrast, the Mn(II)-Mn(III) multiline electron paramagnetic resonance (EPR) signal characteristic of the S-2 oxidation state of the OEC was shown to provide a relaxation enhancement pathway for YD*, however less efficient relative to the one provided by the S2-state multiline EPR signal. We also examined the YD * relaxation enhancement characteristics of the EPR-silent oxidation state produced after brief (1-5 min) dark incubation at 0°C of a PSII sample poised to the EPRactive S-2 state. This EPR-silent oxidation state denoted as "0°C incubation" state was shown to possess remarkably similar P1/2 values with the EPR-active S-2 state in the overall examined temperature range (6-20 K). In addition, these values remained unchanged after successive cycles of the OEC between the EPR-active S-2 state and the "0°C incubation" state. The data presented in this work point to the conclusion that the "0°C incubation" state is indeed an S-2 oxidation state with half-integer spin.

Language:

Multiple languages

Rights:

http://creativecommons.org/licenses/by-nc-sa/4.0/
policy:public

Coverage:

567-574

Source:

Photosynthetica | 2009 Volume:47 | Number:4

Harvested from:

CDK

Metadata only:

false